“This isn't simply an exercise in wildlife conservation,” he said. “If we don't do something to save the ocean now, it won't be just the sharks and the dolphins that suffer. It will be our children and our grandchildren."

DiCaprio was in attendance for the "Our Oceans" conference - a two-day event at the State Department hosted by Secretary of State John Kerry. The conference was created to address a number of critical issues to ocean conservation, with a focus on sustainable fisheries, marine pollution, and ocean acidification. DiCaprio told those attendees that from the beginning, he's been passionate about helping the world's oceans and its creatures.

"As a kid, I always had a fascination with the ocean and its wildlife," he said. "In fact, the first philanthropic dollar I ever contributed was to save the wild manatee in Florida.

"Since my very first dive in the Great Barrier Reef in Australia 20 years ago to the dive I got to do in the very same location just two years ago, I’ve witnessed environmental devastation firsthand," he added.

In introducing the actor, Kerry praised DiCaprio for showing genuine passion, leadership, and commitment to helping the world's oceans.

"I was very, very struck during the course of our time together about his seriousness of purpose," he said. "He doesn’t just lend his name to this kind of an effort casually. He does his homework. He knows the issues. He invests time to visit places where he can learn more about those issues. And he understands how to make the case effectively and persuasively."